1. Field of the Invention
The present invention relates to a door handle for a vehicle, and in particular to a door handle suited to be used in a vehicle which includes a transmitter for transmitting a radio signal. The present invention also relates to a smart entry system for a vehicle using the door handle.
2. Description of the Related Art
Conventionally, there is known an electronic key system which remote-controls lock/unlock of a door of a vehicle. For example, an electronic key system disclosed in Japanese Laid-Open Patent Application No. 5-156851 includes a wristwatch provided with a transmitter for generating ultrasonic waves modulated with a code for opening/closing operations of a door of a vehicle. A receiver is provided inside a door panel near the door handle for receiving the ultrasonic waves. The code for the opening/closing operations is demodulated from the received ultrasonic waves, and a key actuator is actuated in accordance with the demodulated code.
Recently, developments have been made of what is called a smart entry system in which a door of a vehicle is unlocked or locked when a user carrying a radio device comes close to or moves away from the vehicle. Such a smart entry system includes an onboard station which is provided on a vehicle and a portable station which is carried by a user. The onboard station transmits a radio request signal, and the portable station transmits a radio response signal including a predetermined code in response to the radio request signal transmitted by the onboard station. When the onboard station receives the radio response signal transmitted by the portable station, the onboard station compares the code included in the received response signal with a specific code. If the received code corresponds to the specific code, the onboard station unlocks the door. Thereafter, when the onboard station no longer receives the radio response signal from the portable station, the door is locked.
In such a smart entry system, if a transmitting antenna of the onboard station is provided inside a metallic door panel as in a case of the above-mentioned conventional electronic key system, an area in which the transmitted signal can reach (hereinafter referred to as a transmission area Ai) becomes narrower as shown in FIG. 1 for a higher frequency of the transmitted signal since the transmitted signal is shaded by the door panel to a greater extent. Thus, in order to enlarge the transmission area Ai, it is necessary to use a low frequency or large output power for the radio signal to be transmitted. In this case, a scale of a transmission circuit becomes larger and a cost of the system increases.
It is a first object of the present invention to provide a door handle for a vehicle which can miniaturize a transmitter provided on the vehicle and reduce a cost of the system.
It is a second object of the present invention to provide a smart entry system for a vehicle which can miniaturize a transmitter of an onboard station and reduce a cost of the system.
The first object of the present invention can be achieved by a door handle for a vehicle, the door handle comprising:
a handle body which is mounted on an outer face of a door of the vehicle; and
at least a transmitting antenna of a transmitter which transmits a radio signal toward outside of the vehicle, the at least a transmitting antenna being integrated with the handle body.
The second object of the present invention can be achieved by a smart entry system for a vehicle which includes an onboard station and a portable station, wherein the onboard station comprises:
a transmitter for transmitting a radio request signal via a transmitting antenna, at least the transmitting antenna being integrated with a door handle of the vehicle which is mounted on an outer face of a door of the vehicle; and
a receiver for receiving a radio response signal via a receiving antenna transmitted from the portable station in response to the radio request signal.
According to the inventions, since the radio signal is transmitted from the transmitting antenna which is integrated with the door handle mounted on an outer face of the door, the transmitted radio signal is not shaded by an outer door panel of the door. Accordingly, the radio signal can be transmitted from the antenna with a high efficiency without usage of a high frequency or a large output power. Thus, it is possible to miniaturize the transmitter and reduce a cost of the system while achieving a wide transmission area.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.